1. Field of the Invention
This invention relates to the manufacturing of integrated circuits and, in particular, to the surface finishing of integrated circuit die surfaces prior to emission analysis.
2. Description of Related Art
Microprocessor chips or dies are made from semiconductor wafers and contain numerous integrated circuits. Various methods are used for the identification, redesign and process improvements to functioning and non-functioning integrated circuits. These methods include functional characterization of logic integrated circuits for design debug, earlier hardware functionality, reliability qualification assurance, and manufacturing yield learning analysis. Such methods require backside emission microscopy, laser optical beam induced current (OBIC), light induced voltage alteration (LIVA), and picosecond image circuit analysis (PICA). Backside emission microscopy involves detecting photons of light from the recombination and relaxation of electrons and holes, typically during semiconductor failure modes. Common techniques to improve infrared wavelength signal of photons emitted from electron-hole pairs of device junctions is to backside thin substrate of silicon to minimized scattering effects of implant dopant concentrations. A tool and process for machining the backside of a silicon semiconductor for backside emission microscope detection is disclosed in U.S. Pat. No. 5,698,474, the disclosure of which is hereby incorporated by reference.
Current techniques use numerical controlled milling machine followed by various methods of hand polishing, chemical-mechanical polishing (CMP) slurries, wet etching, all aimed to remove machine milling marks and scratches. These techniques are unsatisfactory due to the irregularities in hand polishing or hand held machine surface polishing, and to deficiencies in the slurries associated with chemical-mechanical polishing. The problems are exacerbated by the size of the microprocessor chip or die surface, which may be greater than 15 mm by 15 mm, and up to 30 mm by 30 mm or more.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a method of polishing a wafer which provides a surface finish which is uniformly planar.
Another object of the present invention is to provide an improved method and tool for removing milling machine marks from die surfaces.
A further object of the invention is to provide a faster time interval for polishing a silicon wafer.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.